Implementation of a wet-day frequency correction

Quantile-mapping can be preceeded by a wet-day frequency correction that tries to level the number of wet-days in both reference and climate model data before the actual bias-adjustment is done. Two approaches have been suggested: 1) ssr and 2) wd_numwet. Peter Berg or Thomas Bosshard can give more details about the methods. Method 1) in particular has the potential to deal with dry-frequency-bias, i.e. to increase the number of wet-days in climate model data.

Relevant reference of the method: Vrac et al. (2016), doi:10.1002/2015JD024511